IS 3873 : 1893 REAFFIRMED ~/ 1nnl ~ ~ ~G Cfim/~~ ~ ~T--URr~ ( F''U ~~Q( ) m ~ 3ffif~ Indian Standard LAYING .CEMENT CONCRETE/STONE SLAB LINING ON CANALS - CODE OF PRACTICE ( Second Revision) UDC 626·823-914: 006 I) DIS 1993 BUREAU OF INDIAN STANDARDS MANAIC BHAVAN, 9 BAHADUR SHAH ZAFAR MARO NEW DELHI 110002 ~:? ",' July 1993 Prlee G....,4 AMENDMENT NO. 1 SEPTEMBER 200~ TO IS 3873: 1993 LAYING OF CEMENT CONCRETFJ STONE SLAB LINING ON CANALS - CODE OF PRACfICE ( SecorulRnUIon) ( Ptlge 1, cloue 2, References ) - Insert the fol1owill8 It the appmprilte place:' CIS 9698: 1995 UniDg of Clnals with polyethyleae film , (flnl ~ision)' Code of praclice ( P4,e 4, claUM! 5.5, J'GrG 1, lina 26 to 30 ) - Substitute 'For )Iying of polyetbyleDC film., lefc~nce may2be made to IS 9698t for 'The fonowing properties _.··.······9.5 N/mm '. ( Page 4, Nole) - Delete. (WRD13 ) Irrigation Canals and Canal Linings Sectional Committee RVD 13 FOREWORD This Indian Standard was adopted by the Bureau of Indian Standards, after the draft finalized by the Irrigation Canals and Canal Linings Sectional Committee had been approved by the River Valley Division Council. This standard was first published in 1966 and subsequently reviled in 1978. This second revision has been made in view of the experience gained during the course of these years in use of this standard. In this revision the scope of standard has been enlarged so as to cover precast cement' concrete tiles/stone slabs. The text has been updated by making reference to latest version of standards. · J Lining of canals is considered an important feature of irrigation projects as it not only minimizes the loss of water due to seepage but also results in achieving considerable economy in the use of cultivable land which would otherwise be prone to waterlogging due to rise in water table. Further, the water thus saved can be usefully employed for the extension and improvement of irrigation facilities. Lining of water courses in the area irrigated by tube wells assumes special significance as the pumped water supply is relatively more costly. Lining of canals permits the adoption of high velocities resulting in proportionate savings of the cross-sectional areas of the channel and land width required with corresponding saving in the cost of excavation and masonry work, which may in certain cases offset completely the extra . cost of lining. Also, the lining ensures stability of channel sections thereby reducing the maintenance cost. Lining of canals in erodible soils helps in maintaining regime. Lining prevents rodents and other burrowing animals from digging holes in the embankments and causing canal breaches. The benefits that accrue from lining canals generally justify the initial capital cost and because of this there is now better appreciation of the need for lining on canals. Judicious selection of serviceable and economical lining at the first instance and subsequently proper execution of the work while laying the canal lining reflects considerably in achieving overall economy in the project. Guidance with regard to the selection of canal lining for any particular canal is given in IS 10430 : 1982 'Criteria for design of lined canals and guidelines for selection of type of lining'. However, having once decided to adopt lining in any particular canal, this standard would give necessary guidance in laying cement concrete ( cast In-situ and precast) and stone slab lining. IS 3873 : 1993 Indian Standard LAYING CEMENT CONCRETE/STONE SLAB LINING ON CANALS - CODE OF PRACTICE ( Second Revision) 1 SCOPE This standard covers lining on canals using plain cement concrete in-situ/precast and stone slabs. 2 REFERENCES The Indian Standards listed below are necessary adjuncts to this standard: 3.2 Consolidation The gradual reduction in volume of a soil resulting from an increase in compressive stresses. 3.3 Construction Joint A joint occurring in a structure composed of homogeneous material, such as earth or concrete, along a plane or surface formed by cessation of placing of material for a time, such as overnight or for several days. IS No. 456 : 1978 1128 : 1974 Title Code of practice for plain and reinforced concrete (third revision) Specification for linestone ( slabs and tiles) (first revision) 2720 Methods of test for soils: ( Part 7 ) : 1980 Part 7 Determination of water content--dry density relation using light compaction ( second 3.4 Expansion Joint A joint provided in exposed members between fixed points to permit vertical movement where differential settlement is anticipated. 3.5 Lip Cutting Cutting of the extra width provided at the inner face of the bank under compaction to allow for revision) any lapses in compaction due to the inability of Specification for bitumen sheep-foot rollers to cover the edge of the bank 3384 : 1985 primer for use in waterproof- resulting from the safe limits set by different ing and damp-proofing (first operators of compaction machinery. revision) 3.6 Slip..l.orm Specification for sandstone 3622 : 1977 (slabs and tiles) (first revision) A steel plate provided at the leading edge of the Code of practice for under- slip-form machine, extending across the bottom 4558 : 1983 drainage of lined canals (first and up the slopes of the canals to form the finished surface of the lining. revision) Guidelines for lining of canals 3.7 Subgrade 9451 : 1985 in expansive soils (first revision) Specially prepared canal profile for placement Criteria for design of lined of lining. 10430 ; 1982 canals and guidelines for 4 PREPARATION OF SUBGRADE selection of lining 4.1 Expansive Soils Specification for precast 10466 : 1991 cement concrete tiles for canal The detailed position in this regard is given in IS 9451 : 1985. lining (first revision) 4.1.1 If the expansive clay is in thin layers or 3 TERMINOLOGY in small pockets in an otherwise suitable 3.0 For the purpose of this standard, the subgrade it should be over-excavated and replaced with a suitable non-expansive soil and following definitions shall apply. compacted suitably. 3.1 Compaction 4.2 Preparation of Subgradc Consisting of Rock The densification of a soil by means of The subgrade in rock should be excavated mechanical manipulation. to the required cross section. Over excavation 1 IS 3873 : 1993 in rock is generally unavoidable and should be minimized by using wedging and barring methods, for final dressing. 4.2.1 Over-excavation in hard strata having side slopes more than 1 : 1 beyond the profile line may be backfilled with gravel and aggregate, large aggregate forming the bulk of backfill with smaller aggregate filling the voids and a layer of pea gravel as binding material. The bed may then be compacted with road rollers and sides with rammers to form a firm backing for the lining. For over excavation in hard strata having side slope less than 1 : 1, beyond the profile, the backfilling may be suitably done with chip masonry or lean concrete. However, for bed the backfilling may be done with properly compacted murum. Over excavation up to 5 em may be backfilled. If over excavation is up to 10 cm lean concrete may be used. Beyond 10 cm backfilling with chip masonry is preferable. 4.2.2 For slip-form paving, over excavation up to 10 to 15 cm may be required. Such overexcavation may be backfilled with selected material and compacted at optimum moisture. The material selected should be machine trimmable and be gravel/stone-free earth. 4.2.3 Tolerance in Excavation Excavated profile provides the final base for the lining and the tolerance should be comparable to those required for paving. Departure from established alignment: ± 20 mm on straight section, ± 50 mm 011 tangents, and ± 100 mm on curves. Departure from established grade: ± 20 mm. 4.3 Preparation of Subgrade Consisting of Soil The subgrade should be prepared, dressed and rolled true to level and according to the required cross-section of the canal to form a firm compacted subgrade for the lining. 4.3.1 In other than predominantly sandy reaches where the dry bulk density of the natural soil is not less than 1·8 g/cm8 , initial excavation should be done up to about 30 em above the final section and the cutting to final shape should be done immediately before established centre line of the canal and the corresponding design levels. For verifying the slope of the templates representing the sample profiles the diagonals of the cross-section of canal, between the two opposite side templates are checked. After laying the templates to the correct profile a cord should be stretched over the two templates (representing the same profiles) and run along the slope till the surface between the two profiles is properly levelled and dressed from top to bottom. 4.3.3 [f at any point material of prepared subgrade has been excavated, beyond the neat lines required to receive lining, the excess excavation should be filled with graded filter material compatible with subgrade material and thoroughly compacted in accordance with 4.3.5 and 4.3.6. ~.3.3.1 IS When partial filling of an existing canal necessary to adequately reduce the crosssectional area to that required for lined canal, the fill should be placed and suitably compacted to avoid its settlement and rupture of the lining. 4.~.4 To cover up any lapses in the compaction of the inner core of the banks near the edges and to allow sufficient width for a labourer to work conveniently a lip cutting width of not less than SO em horizontally should be provided. Depending upon the nature of soil and the side slo~es of the canal, the lip cutting width may be In the range of 50 to 100 em. For canals in embankment it should be ensured that one monsoon is passed for proper consolidation before lining is done. 4.3.5 Compaction of Subgrade Predominantly Sandy Reaches 4.3.5.1 Bed The compaction of the bed should be done by over-saturating the bed by flooding it with water before lining is laid. 4.3.5.2 Sides The compaction of sides should be done by over-cutting the subgrade by 15 em and refilling it with lean mortar with adequate quantities of lime or cement or by vibrocompactors. lining. 4.3.2 For checking the uniformity of side slopes, sample proftles at an interval of about 20 m, in straight reaches and 10 m in curved reaches should be made. Concrete templates of suitable size should be laid on the sample profiles. To begin with the top and bottom of the side templates should be fixed with reference to the 2 4.3.6 Compaction of Subgrade in Other than Predominantly Sandy Reaches All compaction should be done at optimum moisture content in layers not more than 15 em thick to obtain a dry bulk densi ty of not less than 95 percent of the density at optimum moisture content obtained in accordance with IS 2720 ( Part 7 ) : 1980. 4.3.6.1 Where the dry bulk density of the natural soil is equal to or more than 1·8 g/em s, IS 3873 : 1993 the procedure described in 4.3.1 should followed. be 4.3.6.2 Bed Where the dry bulk density of the natural soil is less than 1·8 g/cm 3 and the subsoil water is near the subgrade, the consolidation should be done by under cutting the bed by 7·5 em and then ploughing up to 15 em below the subgrade level. The loosened soil should then be recompacted with sheep foot rollers or other suitable devices. Where the subsoil water is low, requiring no dewatering and the dry bulk density of the natural soil is less than 1·8 g/cm8 , the consolidation should be . done by digging the canal up to subgrade level and after loosening the earth below subgrade up to 15 em by disc harrows, or ploughing and compacting the same to a depth of 11 em. After that, the second layer of IS em of earth should be laid over the compacted layer by taking earth from lip cutting and compacting this to a depth of 11 em. The compacted layer of 7 em above the subgrade level should be removed and the subgrade brought to design profile before laying the lining, 4.5.1 Before spraying crude oil, subgrade should be perfectly dry, clean and free from dirt. and crude oil should be allowed to penetrate the subgrade surface. Bitumen should be heated to a temperature of 175°C and appiled to the subgrade by a suitable sprayer. Immediately following the application of bitumen, dry sand should be uniformly spread. Lining should be started 6-12 hours after spraying. 5 LAYING OF IN-SITU CONCRETE LINING S.O The concrete used for lining should be design mlx concrete of grade M 10 or M 15 and should conform to requirement of IS 456: 1978. · I. · · , ···· S.1 Slump For hand-placing and for placing with light machines where concrete is screeded from bottom to the top of the slope, the consistency should be such that the concrete will barely stay on the slope. A slump of 60 to 70 mm should be generally allowed. For heavier, longitudinally operating slip-form machines, a slump of 50 mm at the laying point should be used. To have a close control of consistency and workability of the concrete, the slumps of concrete should not vary more than 20 mm which would, otherwise, interfere with the progress and quality of the work. 5.2 Thickness 4.3.6.3 Sides Consolidation on sides should be done, by manual labour or suitable compactors to a depth of 30 em to obtain a minimum dry bulk density of not less than 90 percent of the density at optimum moisture content. 4.4 1JnderdrainaRe For a lined canal where the ground water level is higher or likely to be higher than water level inside the canal so as to cause damaging differential pressure on the linings; or where the subgrade is sufficiently impermeable to prevent free drainage of the underside of lining in case of rapid draw down, underdrainage should be provided in accordance with IS 4558 : 1983. 4.5 Anti-salt Treatment Soil in all reaches should be tested for salt content before the lining is started. Where the salt content is over 1·00 percent or sodium sulphate is over 0·36 percent, the subgrade should be first covered wi th about 2 mm thick layer of bitumen obtained by evenly spraying bitumen at a rate of about 2·35 kg/mi. To get a good bond between bitumen and soil, crude oil at a rate of 60·5 lit/m" should be sprayed over it in advance of spraying bitumen. In case such a situation is encountered only in small packets the replacement of subgrade up to a suitable depth by suitable earth from adjoining reaches should be considered, if economical. The thickness of lining should be fixed depending upon the nature of the canal requirement, namely, hydel channel or irrigation channel, full supply depth and channel capacity. Hydel channel should have a greater thickness than channels meant for irrigation because of drawdown effects and where closure for repairs may not be usual. Deeper channels should have greater thickness than shallow depth channels. Minimum thickness of canal lining based on canal capacities are given in Table 1. Table 1 Thickness of In-Situ Concrete Lining Depth of Water (2) Capacity of Canal (I) (cumecs j 0-5 5-50 50..200 200-300 300·700 Thickneu of Lining (3) m 0-1 mm SO~60 1-2.S 2-5.4'5 4 5·6·5 6'5-9-0 60-75 75-100 90·100 120.150 NOTE - If surface deterioration in freezing climate is expected, these thick.iesscs may be increased. The lir.i.1g will not be subjected to external hydrostatic ca I th pressures or uplift caused by expansive clays or frost heave, 3 IS 3873 : 1993 5.3 Tolerance in Concrete Thickness, Alignment and Grade a) Departure from established alignment 20 mm on straight reaches ± 50 mm on partial curves or tangents In case fil ter material is to be pi ovided over subgr adc to take care of differential .hydro~ta tic pressure and draw-down in canals, designs of coarse filter material blanket immediately in contact with lining would be necessary. To make such filter blanket effective and to prevent ingress of concrete into it, before placement of concrete, polythene sheet should be placed over the filter blanket. All concrete should be placed directly in its' final position within 20 minutes of mixing, Concrete should not be dropped fr. m excessive height and free fall should be kept to a minimum to avoid segregation. Construction should be continued until satisfactory construction joint is made. Concrete should not be placed faster than the placing ± b) Departure from established grade c) Variation in concrete, lining thickness ± 20 film on small canals 10 mm provided average thickness is not less than speci- ± fied thiokness 5.4 Mimi Concrete should normally be mixed in nical mixer. ~.5 crew can compact it properly. 5.5.1 Hand Placing Hand placing of concrete should normally be adopted where cheap labour is available. a mecha- Placing , Placing of concrete should not be started until all formwork, installation of parts to be embedded and preparation of surfaces upon which concrete is to be laid have been completed. All absorptive surfaces against which concrete is to be laid should be moistened thoroughly so that moisture will not be withdrawn from freshly placed concrete. The surfaces however, should be free from standing water and mud and 1: 3 cement slurry shall be spread over the moist subgrade before placing concrete to prevent absorption of water from 'concrete making it spongy. A plastic membrane of low density polythene film of suitable thickness may be used below the concrete lining in sides and in beds where the subgrade of the lining is of pervious materials like murum etc so as to prevent absorption of water in sUbgrade from green concrete, during placement on the subgrade. The approved film is to be laid on the neatly w~J1 dressed subgrade, and fixed in the subgrade so as to prevent displacement during the placement of the concrete. The use of polytheue sheets is for achieving better ultimate imperviousness of the lining as a whole. The following properties of L. D. P. E. film are given as guidelines with deviation to the extent of ( plus or minus) 10 percent. 1) Tensile strength 2) Tear resistance 17·5 N/mml 9·5 N/Jnm 2 5.5. t.l Depending upon the construction method and arr.mgernent of concreting, the sequence of placing concrete either on the sides or the bed should be decided. It is preferable to place concrete on the sides first if the concreting equipment and the construction materials like aggregate, sand etc, are kept on the ca!1al bed. This will prevent the bed from getting spoiled by the subsequent concreting operations for the sides. Other things being equal placement for bed first should be preferred. 5 5.1.2 The concreting of the sides and bed should be done in alternate panels. The panel width should vary from 2 to 3 m. In no case should the panel width exceed more than 3 m as wider bays require unwieldy vibrators for compaction. The constru~tion joints sh.ould. be either parallel or perpendicular to the direction of flow. In case the full supply depth is high, construction joints along r'ie direction of flow to divide the length of the panel should be provided. For this purpose wooden rafters should be used. The succeeding panels should be laid at an interval of one day. If the sloping length is less than 2·5 to 3 metres, concrete should be placed in one operation over the entire length. In case of deeper canals where the sloping length is more it should be suitably divided (say for a length of about 2 metres) in each alternate panel so as to prevent appreciable downward flow of concrete. The bays/panels should be formed by proper form-work of M. S. channels laid all around the bay. The channels should be firmly spiked to the subgrade so that no movement takes place NOTE - Till better materials are developed, use of LOPE fllm of appropriate strength and resistance against slippage of tunnel may be adopted as a second line of defence against embankment failure and a~ a seepage barrier parttcularly in high capacity channels of relatively bigger depth. 4 IS 3873 : 1993 at the time of concreting and vibration. The depth of the. M. S. channels should correspond to the required thickness of concrete lining. The concrete should be dumped in the bay from bottom to top and the n spread all over the bay uniformly and to the required thickness guided by the channels. The spread concrete should then be compacted properly and thoroughly by means of mechanical or screed vibrators. An improvised plate vibrator operated by high horse power engine and a winch for moving the vibrator up the inclined slope should be made use of for proper compaction. When width of panel is less i, e. up to 2 m manual operation of vibrators is possible and may be permitted. In no case the concrete should be compacted by tamping. The compacted surface should be true to the required side slope. Before re-using the channel forms, they should be thoroughly cleaned and well o!led .. Care should be taken, while placing and vibrating the concrete that, the sub-grade in the adjacent bays does not get spoiled. 5.5.1.3 For bed lining the procedure for laying the concrete on the canal beds should be same as that for sid e lining except the operations specifically required on sloping SUI faces. The compaction should be done by m ans of a heavy screed vibrator moving on the side channels. 5.5.1.4 In order to test the effectiveness of vibration, permeability and strength of concret.e cores at suitable places from the side as well as from the bed concrete should be taken. 5.~.1.5 ~_ 1 .. FlO. 1 SIDES CAST FiRST . ~FIG. 2 ;::r:r~ .... _......,...""'1 BEU CAST FIRST 5.5.2 Mechanical Placing 0.( Concrete Concrete for slip-form should be air entrained to provide a m?re workable and slippable mix. Percentage of air should be as follows: Maximum Aggregate Size, mm 10 Air, Percent by Volume 8·0 7·0 6·0 5·0 12·5 20 25 40 4·5 Air entraining agents win always be used in concrete by means of slip-form paving machine for entraining air. 5.5.2.1 Subgrade guided slip-form This should be used for lining small to moderate size canals. The slip-form should be supported directly on the subgrade and operated lungitudinally along it, concrete should be screcded on the bed along the canal and on the sides from bottom to top. Tn-situ sleepers in case of bed, and precast in case of sides, should be provided under the joints. The sleepers should be 20 em wide The sleepers should be placed centrally below the joint. Concrete used for sleepers should be of the same grade as for lining. Alternatively brick sleepers 225 x 150 mm with 1:4 mortar may be used. Concreting near the joints should be done with utmost care so as to avoid segregation and collection of loose pieces of aggregate along the formwork which may later result in honey- and 15 ern deep. 5.5.2.2 Rail guided slip-form . They are adopted for larger canals of considering length. Slip-forms supported on rails placed along both berms of the canals should be operated longitudinally. Concrete should be spread uniformly on the bed longitudinally and on the sides from bottom to top. combing. 5.5.1.7 Concreting near the junction of the side concrete and b d concreting should be done such that both should rest firmly against each other to resist any back-kick from external hydrostatic forces ( see Pig. 1 and 2). The sketches indicate the procedure for formation junction of the sides with bed depending upon the sequence laying concrete i.e. sides first and vice-versa. 5.6 Finishing The SUI face of concrete finished against forms should be smooth and should be free from projections, honeycombing and other objectionable defects. Immediately on the removal of forms, all unsightly t idges or lips should be removed and uidesirable local bulging on exposed surfaces should be remedied by tooling and rubbing. Repairs to concrete surfaces and or 5 IS 3873 : 1993 additions, where required, should be made by cutting regular openings into the concrete and placing fresh concrete to the required lines. 'The chipped openings should be sharp and should not be less than 70 mm in depth. The fresh concrete should be reinforced with wire mesh extending to the full depth of the slab and chipped and trowelled to the surface of the openings. The mortar should be placed in layers not more than 20 mm in thickness after being compacted and each layer should be compacted thoroughly. All exposed concrete surface should be cleaned of impurities, Jumps of mortar or grout and unsightly stains. lining. The top surface of the key should be finished with a downward slope of 1 in 10 or so towards the canal. A day after completion of concreting of all panels between two templates, concreting of key slab should be done. Concurrently with the curing operation, surface drainage arrangement of the bank such as construction of keys, bank surface slope away from the lining and construction of longitudinal drain on the outer wedge shall be completed. This is necessary to prevent surface and subgrade erosion and consequent damage to lining. ta, S.' Joints 5.9.1 Expansion Joints These should not be provided except where a structure intersect is the canal. The details are given in relevant Indian Standards covering such structures. 5.6.1 The concrete should be finished to an even and smooth surface free from pockets, voids or exposed aggregates. This should be obtained by careful use of a long-handled steel trowel. Any remaining roughness or rough spots shall be rendered smooth, without any time interval after laying the concrete, with cement mortar of 1 : 3 proportion. S.7 Curing Subsequent to laying of concrete lining and after a period of 12 hours, the lining should be cured for at least 28 days. S.9.2 Construction Joints Construction joints form a weak link in the lining and deterioration is generally noticed at such joints. Besides joints are potential seepage points for the canal water. As such, number of joints should be kept to the minimum and great care should be taken to obtain well compacted 5.7.1 Bed Lining and smooth concrete surface at joints. To Twelve hours after laying of concrete, small ensure a good surface the shuttering should be bunds longitudinal and cross-wise consisting of smooth, cleaned, well oiled and rigidly fixed at earth materials or lean mortar ( I : 15 ) should site. Besides different mechanisms for compacbe laid for 'U height of 8 em for the purpose of tion of concrete in lining, tamping with iron curing. Water will be kept always ponded in bar near the joint surface gives better results. these bunds for 28 days continuously. To cater for initial shrinkage and cracks, concreting should be done in alternate panels S.7.2 Side Lining The panel in which concreting is done the pre- or bays. The panel size for the bed and slope vious day should be covered with burlap or of the canal should be adopted as given in 5.5. 25 em wide L.D.P.E film of 150 micron thickness empty cement gunny bags. should be placed on the top of sleepers, providFor the purpose of curing, water tank of 5 000 ed to support construction joints. The top of litres capacity should be placed on a platform at film and side of panel should be applied with the edge of service road at the rate of one printer conforming to IS 3384 : 1985. This sheet for 500 m length of lining, which should be kept acts as an intercepter for seepage through the filled with water, with arrangement of outlet joint. In case lining is laid by mechanical paver, and flexible hose of at least 300 m length. PVC water stops are placed at joints along with Water should be continuously sprinkled on the · the concreting. The water stops in such a case gunny bags or hessian cloth keeping them wet should be provided at a spacing not more than 4 for 28 days. Sprinkling shall be done during metres centre to centre. night time also. The curing of side slopes may be done by constructing masonry drains with weep 6 LAYING OF PRECAST CONCREfE TILES/ boles or perforated pipes on the coping at the STONE SLAB LINING top of lining or by sprinklers. 6.1 The tile should conform to IS 10646: 1991 and stone slab to IS ) 128 : 1974 or IS 3622 : 5.8 Surface Drainage 1977 of length 0·45 to 0 90 em, width 0·45 m The top of the side lining concrete should be and thickness 35 to 50 mm. keyed into the subgrade both in cutting as well as banking by taking it horizontally for a 6.1 The lining should be started only when at width of about 300 mm, This key would prevent least 3S m length of canals subgrade is 'properly direct entry of surface rain water behind the dressed to receive lining. The arrangement 6 IS 3873 : 1993 for mortar and availability of sufficient number of tiles/stone slabs should be ensured before starting the work. 6.3 The subgrade should then be uniformly soaked with water without making it slushy to ensure that water penetrates to a depth of about 300 mm in sandy soil and about 150 mm in other soils. Wetting of subgrade should continue in advance of laying of tiles so that soil does not absorb moisture from the mortar laid on the subgrade on laying the layer of tiles. 6.6 On completion of laying lining should be kept wet by sprinkling water over it to keep the mortar wetted. On the next day, the surface should be kept wet and joints should be carefully wetted. Hollow joints should be raked to a depth of 12 rom, loose mortar removed from sides and top of tiles/ stone slabs and the joints properly refilled. Loose tiles/stone slab should be removed and relaid. 6.8 The complete lining should be checked for level with wooden templates and spirit levels. 7 SAFETY LADDERS 7.1 Safety ladders should be constructed in canal lining as directed by the engineer-incharge. 7.1.1 Safety ladders consisting of ladder rungs should be constructed in canal lining about 30 m upstream of the point where the canal enters some underground structure. In other reaches safety ladders may be provided at a spacing of about 300 m; the ladders being provided alternatively on either side. 7.1.2 Ladder rungs should be smooth, round mild steel bars, galvanized or coated with coaltar after installation. 7.2 Typical details illustrated in Fig. 3. of safety ladder are 6.4 Single tiles/stone slab profile of lining parallel to central line of the canal should be prepared at suitable intervals. Mortar ( 1 : 3 ) should uniformly be spread over subgrade for a minimum thickness of 12 mm and the tiles should be properly laid in position quickly. It should be ensured that vertical joints are completely filled with mortar. The tiles should be laid in bed with their lengths at right angles to the central line of the canal while on the other side slopes they should be laid parallel to the central line. Tiles should be firmly embedded in mortar. Hollows, jf any, should be rectified by relaying defective portion with fresh mortar. The tiles should be laid over a minimum of 12 mm thick cement mortar and having aggregate less than 6 rom to bring overall fineness modulus less than 2. Hollow the joints should be raked and pointed with the same mortar. The thickness of joint should be 20 to 25 .mm. 6.5 Stone slabs should be firmly embedded in mortar. Hollows if any should -be rectified by relaying the defective portions with fresh mortar. As an alternative to safety ladders steps of rise 150 mm, tread 300 m and 1 500 mm wide may be provided in plain cement concrete of grade M-IO at a spacing of 300 m centre to centre ( staggered) on either side of canal. Details of the steps are illustrated in Fig. 4. 7 'IS 3873 : 1993 ENLARGED SECTION All dimensions in millirnetres, FIG.3 DETAILS OF SAFElY LADDERS SIDE LrNING RAIL GUIOEWAl.L I I I I I CANAL BED' ., I I . t. PLPE gpANSION JOINT" CEMENT CONCRETE I - - - - - - - - - - - - - - -' - - .... -- - - - _ .... -- ----. - - - - -- - - - - - -- - - - - - -- -- -.-. -.. ~ -. ~ ~ ~ All dimensionl in millimetres. FlOe 4 DETAILS 0' STErS Studard Mark The use of the Standard Mark is governed by the provisione of the Bur~1IU oflrulUl1l Standa,ds Act, 1986 and the Rules and Regulatioas made thereunder. The Standard Mart on products covered by an Indian Standard convey. the assurance that they have been produced to comply with the requirements of that standard under a well defined system of inspection, testinl and quality control which i. deviled and supervised by BIS and operated by the producer. Standard marked products are also continuously eheked by BIS for conrormlty to that standard as a further safeguard. Details of conditions under which a licence for the use of the Standard Mark may be Iranted to manufacturer. or producers may be obtained from the Bureau of Indian Standards. 8llrea··f IIMII . . Stalllladl BIS il a statutory institution established under the . , . . . oj l1Ul1tM I t " ' . Act, 1916 to promote harmonious development of the activities of standardizatioD, markinl and quality certification of goods and attendin, to connected matters in the country. c."npt BIS has the copyright of all its publications. 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